Replace locally-defined keys and values with constants from MediaCodec API (MediaFormat.KEY_..., etc). Value of a constant field is resolved at compile time according to 13.1.1 [1]. I.e., it is safe to reference a constant field not available in older API (MediaCodec API ignores unrecognized MediaFormat.KEY_ values). [1] https://docs.oracle.com/javase/specs/jls/se20/html/jls-13.html#jls-13.1 Bug: none Change-Id: I3c63cfd67cc22db1b957f908508b434d36d88806 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/298940 Commit-Queue: Sergey Silkin <ssilkin@webrtc.org> Reviewed-by: Linus Nilsson <lnilsson@webrtc.org> Cr-Commit-Position: refs/heads/main@{#39668}